A multi-shaft type gas turbine having driving shafts of two or more is known. For example, a two shaft gas turbine has a high pressure side shaft arranged in an upstream side and a low pressure side shaft arranged in a downstream side. The low pressure side shaft is connected to, for example, a load like a compressor.
During the stop condition of a two shaft gas turbine, a turning operation which rotates the shaft at a low speed by a motor is carried out in order to suppress the thermal deformation of the shaft, and so on. The low pressure side shaft is, in general, not required to carry out turning, mainly because of the shortness of the shaft.
In Patent Document 1, a technique regarding the turning of a low pressure rotor of a gas turbine with two shafts is described.